Whole-body photoscans will be used to detect the presence of radiolabeled antibody complexed to a human tumor-associated antigen, carcinoembryonic antigen (CEA). Antibodies prepared in goats, rabbits and monkeys to CEA will be labeled with radioiodine and purified from cross-localizing antibodies by in vitro and in vivo procedures. The tumor localizing capacity of these preparations will be evaluated by administering them to hamsters and monkeys bearing CEA-producing human colonic carcinomas of the GW-39 tumor system and regularly performing whole-body photoscans, as well as by determining tissue radioactivity during and at the termination of each experiment. These experiments are designed to evaluate the metabolism and kinetics of allogeneic and heterospecific tumor-localizing radioantibodies in primate and rodent systems as preliminary work to clinical trials. These studies will consider such factors as choice of the label, labeling procedure, capacity of the antibody to retain its tumor-binding property after coming into contact with the host's plasma and tissues, whether the radioantibody is inactivated by certain levels of circulating antigen, and the possible engagement of localizing sites on the tumor because of prior complexing with circulating antibodies, should these be present.